Re: [Gnuplot-info] explanation to a short script

[Thomas S. <t.s...@fz...>]

the script correctly identifies 0.1 as the minimum, yes,
but not for all data points.
you may have noticed that the 1st three y-values in the plot are '1',
but should be '0.09', '0.045', and '1'.

the script searches for the minimum by storing the actual y-value if
it's smaller than a previous one. as long as the absolute minimum
isn't found, i.e. the data line with the minumum y-value hasn't been
yet read, y-values are divided by the intermediate minimum.
that's the reason why the y-values are always '1' when reading
my data set.


bsmile wrote:
> 
> Dear Thomas,
> 
> I actually specifically checked whether the first script could capture a
> minimum hidden in the data except for the first line. The sample data I
> used
> is
> 
> 1  0.9
> 2  0.45
> 3  0.1
> 4  0.94
> 5  0.44
> 6  0.12
> 7  0.36
> 
> and it seems a single pass corrected identified 0.1 as the minimum. As to
> your sample data, the missing of y range is a 2nd mysterious to me as if I
> change the data to float, it works fine, and even if I interpret the data
> to
> be integer, it should still give the right answer instead of giving
> constant
> 1 for each dataline.
> 
> Sincerely,
> Jon
> 
> 
> On Tue, Feb 15, 2011 at 2:31 AM, Thomas Sefzick
> <t.s...@fz...>wrote:
> 
>>
>> strictly  speaking, nunzio's script only works if the smallest number is
>> in
>> the
>> 1st data line.
>>
>> an example:
>>
>> #ts.dat:
>> 1 10
>> 2 9
>> 3 8
>> 4 7
>> 5 6
>> 6 5
>> 7 4
>> 8 3
>> 9 2
>> 10 1
>>
>> #script:
>> min=10**10
>> grab(x)=x<min?min=x:min=min
>> plot 'ts.dat' using 1:($2/grab($2))
>>
>> gives a horizontal line and a warning about the empty y-range.
>> this means that gnuplot behaves like other programming languages
>> and there is no magic behind it.
>>
>> a 2nd plot gives the correct result, as you have pointed out,
>> because then 'min' already contains the smallest value.
>>
>> #script:
>> min=10**10
>> grab(x)=x<min?min=x:min=min
>> plot "ts.dat" using 1:($2/grab($2)), "" using 1:($2/grab($2))
>>
>> ... , "" using 1:($2/grab($2))
>> is equivalent to
>> ... , "" using 1:($2/min)
>>
>>
>> bsmile wrote:
>> >
>> > Dear Thomas,
>> >
>> > Nunzio Losacco wrote a short script to get each number divided by the
>> > smallest number in a specific column, as
>> > min=10**10
>> > grab(x)=x<min?min=x:min=min
>> > plot 'disy.100' u 1:($3/grab($3))
>> >
>> > I don't quite understand the logic behind although I checked that it
>> works
>> > fine. If I were to do this, I would write something like
>> >
>> > set term dumb
>> > min=10**10
>> > plot 'disy.100' u ($3<min?min=$3:min=min,$1):3
>> >
>> > set term x11
>> > plot 'disy.100' u 1:($3/min)
>> >
>> > and you easily see the idea I wrote it this way. I think this reflects
>> a
>> > big
>> > problem for me to understand deeply how gnuplot deals with datafile and
>> > how
>> > it plots, which is obviously different from the standard programming
>> > languages. Thanks for your in-depth explanation or references,
>> >
>> > Sincerely,
>> > Jon
>> >
>> ------------------------------------------------------------------------------
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>>
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>>
>>
>> ------------------------------------------------------------------------------
>> The ultimate all-in-one performance toolkit: Intel(R) Parallel Studio XE:
>> Pinpoint memory and threading errors before they happen.
>> Find and fix more than 250 security defects in the development cycle.
>> Locate bottlenecks in serial and parallel code that limit performance.
>> http://p.sf.net/sfu/intel-dev2devfeb
>> _______________________________________________
>> gnuplot-info mailing list
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> ------------------------------------------------------------------------------
> The ultimate all-in-one performance toolkit: Intel(R) Parallel Studio XE:
> Pinpoint memory and threading errors before they happen.
> Find and fix more than 250 security defects in the development cycle.
> Locate bottlenecks in serial and parallel code that limit performance.
> http://p.sf.net/sfu/intel-dev2devfeb
> _______________________________________________
> gnuplot-info mailing list
> gnu...@li...
> https://lists.sourceforge.net/lists/listinfo/gnuplot-info
> 
> 

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